CVE-2004-1440: Putty

High severity, CVSS 7.5. EPSS: 4.1% chance of exploitation in the next 30 days.

Multiple heap-based buffer overflows in the modpow function in PuTTY before 0.55 allow (1) remote attackers to execute arbitrary code via an SSH2 packet with a base argument that is larger than the mod argument, which causes the modpow function to write memory before the beginning of its buffer, and (2) remote malicious servers to cause a denial of service (client crash) and possibly execute arbitrary code via a large bignum during authentication.

Affected products

• Putty Putty: version 0.48 only; version 0.49 only; version 0.50 only; version 0.51 only; version 0.52 only; version 0.53 only; …

Published 2004-12-31. Last modified 2026-06-16.